Observing the Solar System Section 20 1 Early

Observing the Solar System Section 20. 1

Early Observations Greek Observations • Saw star patterns in the sky travel together (Constellations)

Early Observations • Some stars seemed to wander (planets) • They were later named by the Romans (Mercury, Venus, Mars, Jupiter, Saturn)

Early Observations • Most Greek astronomers believed that Earth was in the center of a celestial sphere. (geocentric system)

Early Observations Claudius Ptolemy • Earth in center • Planets move on small circle that move on bigger circles • Widely accepted for 1500 years

Early Observations Nicholas Copernicus • Believed in a sun centered system (Heliocentric) Mikolaj Kopernik • Said the planets moved around the sun in circles in 1543

Early Observations Nicholas Copernicus • Was banned by the Catholic church Mikolaj Kopernik Galileo • Used the telescope to support him (Venus phases, Jupiter’s moons) • Was placed under house arrest Galileo

Early Observations Tycho Brahe • Made accurate observation for over 20 years

Early Observations Johannes Kepler • Analyzed Brahe’s observations and found that the path of the orbits were ellipses • Kepler’s 1 st Law

Early Observations Johannes Kepler • He found that the speed of orbiting planets is constantly changing • Kepler’s 2 nd Law

Early Observations Johannes Kepler • When he compared planets, he found a relationship between how far from the sun they were and the time to make one orbit • Kepler’s 3 rd Law

Early Observations Today we know of 8 planets (MVEMJSUN) their moons, and smaller objects that revolve around the sun

What about Pluto? • According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit. • Pluto does not dominate its neighborhood Charon is half it size It does not sweep up its neighborhood, there is much debris in its orbit